Organo(chloro) tin mercaptides



United States Patent US. Cl. 260-4293 7 Claims ABSTRACT OF THE DISCLOSURE These compounds can be depicted by the formula (R) (X) (Z)SnR wherein R is an alkyl group having up to 20 carbon atoms, X is chlorine, R is an alkyl group having at least 5 carbon atoms and Z is selected from the group consisting of R, X, -SR (where R is an alkyl group having 5 to 20 carbon atoms).

This invention relates to certain organotin compounds useful as stabilizers for polymers or copolymers of vinyl chloride. This application is a divisional application of application Ser.No. 489,079, filed Sept. 21, 1965, now abandoned.

Many different types of organotin compounds have been described for use as stabilizers for vinyl chloride polymers in recent years, but nevertheless the search continues for alternative stabilizers which may possess economic and/or technical advantage over those stabilizers already known. Organotin compounds are often believed to stabilize vinyl chloride polymers by acting as scavangers for the hydrogen chloride liberated on thermal or light degradation of the polymer. Accordingly, it has been thought that organotin halides would be inferior organotin compounds for the purpose since they would be expected to be less eflicient in absorbing the hydrogen chloride liberated on degradation than organotin stabilizers containing a direct carbon-halogen bond.

We have now prepared representative members of a class of organotin compounds which are characterized by the presence of at least one tin-halogen bond and at least one tin-sulphur-carbon linkage and, surprisingly, we find them to be efiicient stabilizers for vinyl chloride polymers. Many members of this class of compounds are novel and such compounds constitute a further aspect of the present invention.

Thus from one aspect, the present invention provides a composition comprising a vinyl chloride polymer (which may be a homopolymer or a copolymer which is formed from not more than 20% by weight of other monomers) and from 0.1 to 5% by weight of the polymer of a heat stabilizer having the general formula:

wherein R is a hydrocarbon group, X is a chlorine or bromine, R is an organic group derived from an organo mercapto compound R'SH and Z is an R, X or SR' group or an acyloxy group R"CO derived from an organic carboxylic acid R"CO H.

From a second aspect, the invention provides novel compounds which are included among those which may be used as the heat stabilizers of the first aspect of the invention. These novel compounds are organotin compounds 3,542,825 Patented Nov. 24, 1970 fvhich may be represented by the following general formuwherein R, X and Z are as hereinbefore defined and R' is an organic group having at least 5 carbon atoms which is derived from an organic mercapto compound R SH.

From a third aspect, the invention provides a process for the preparation of the compounds of the invention which comprises reacting substantially stoichiometric amounts of a mono-organotin trihalide or di-organotin dihalide with an organo mercapto compound (of which at least one molecular proportion has at least 5 carbon atoms) and, optionally, a carboxylate salt.

From a fourth aspect, the invention provides a further process for the preparation of those compounds of the invention having the formula X Rn-R'2 z" where R, R and X are as hereinbefore defined and Z is an X or SR group (where R is as hereinbefore defined), which process comprises heating substantially stoichiometric amounts of an organotin mercaptide of the formula R,,Sn(SR'),, (wherein a is 1 or 2 and at least one R group has at least 5 carbon atoms) with at least one tin halide of the formula R SnX (wherein b is 0*, 1 or 2) at a temperature of from 50-200" C. to eflfect a disproportionation reaction. It will be noted that the tin halide may be a monoor di-organotin halide and/or, when appropriate, a stannic halide.

In the general formula for the compounds which may be employed as stabilizers in the compositions of the invention R may be any hydrocarbon group such as an alkyl group having up to 20 carbon atoms, an alkenyl group such as vinyl, or aralkyl group such as benzyl or an aryl group such as phenyl, tolyl or xylyl. However, it is preferred that R shall be an alkyl group having from 4 to 12 carbon atoms, particularly n-butyl or n-octyl. X may represent a bromine or chlorine atom, but preferably for economic reasons it is the latter. The group R is derived from an organic mercapto compound (R'SH). When there is present in the compounds at least one group R which has at least 5 carbon atoms (herein designated where necessary as an R' group), the compounds are novel and constitute the said second aspect of the invention. Preferably the mercapto compound (R'SH) is an alkyl mercaptan in which the alkyl group has from 4 to 20 carbon atoms, particularly octyl, dodecyl, cetyl or stearyl mercaptan, but R may also be derived from alkyl esters of mercapto-carboxylic acids such as, for example, thioglycollic or thiomalic acid, such esters preferably having from 4 to 8 carbon atoms in the alkyl group. The group R may also be derived from a thio-acid or dithioacid of the carboxylic or phosphoric se ries such as, for example, thiobenzoic acid or a dialkyldithiophosphoric acid or a dialkylthiophosphoric acid.

The group Z in the general formula is normally an R, X or SR group which may be different to the other R, X or SR present in the molecule though normally it will be the same. Alternatively, Z may be an acyloXy group R"CO derived from a carboxylic acid (R"CO H). Thus, for example, Z may be derived from aliphatic monocarboxylic acids having from 2 to 20 carbon atoms, particularly acetic, Z-ethylhexoic, n-octoic or lauric acid or from dicarboxylic acids such as maleic or succinic acids or half-esters thereof, e.g. benzylmaleic acid; alternatively Z may be derived from aromatic monocarboxylic acids such as benzoic acid. However, this last-mentioned feature is less preferred and it is most preferred that Z should be a further mercapto-residue.

Accordingly, as representative examples of the compounds which may be employed as stabilizers in the compositions of the invention there may be mentioned the following list (List A):

dibutyl-butylmercapto-tin chloride; butyl-dioctylmercapto-tin chloride; butyl-dioctylmercapto-tin bromide; butyl-dodecylmercapto-tin dichloride; butyl-didodecylmercapto-tin chloride; butyl-dodecylmercapto-tin (thiobenzoate) chloride; octyl-dodecylmercapto-tin chloride; phenyl-dioctylmercapto-tin chloride; butyl-bis-(iso-octylthioglycollate)tin chloride; octyl-bis-(butylthiomaleate)-tin chloride; dibutyl-dodecylmercapto-tin chloride; dibutyl-octylmercapto-tin bromide; di-octyl-dodecylmercapto-tin chloride; di-octyl-iso-octylthioglycollate-tin chloride; butyl-dodecylmercapto-aceto-tin chloride; butyl-dodecylmercapto-lauroyl-tin chloride; and butyl-dodecylmercapto-tin (benzylmaleate) chloride;

all but the first of these compounds are believed to be novel compounds.

The compounds for use as stabilizers in the compositions of the invention may be prepared by reacting a monoor di-organotin halide with an organic mercapto compound (RSH) in an amount insufiicient to react with all the halogen atoms in the organotin halide and, preferably, in the presence of a tertiary amine as hydrogen halide acceptor. Apart from the amounts of reactants, the normal conditions for reacting organotin halide with organic mercapto compounds are employed. Thus, for instance, the organotin halide and mercapto-compound may be mixed and heated together until reaction, as evidenced by the evolution of hydrogen halide, is complete. A reaction temperature of 4070 C. is usually sufficient. However, preferably a hydrogen halide acceptor is present, particularly a tertiary amine such as triethylamine or pyridine. The resulting amine hydrohalide may then be removed from the reaction mixture by filtration or by aqueous extraction. The reaction may also be carried out in an inert solvent medium such as a hydrocarbon or ether solvent. The products are usually liquids and are conveniently purified merely by stripping under vacuum. Some of the compounds may also be purified by vacuum distillation. They are, however, susceptive to solvolysis, at least to some extent when contacted with hydroxylic compounds such as water, acids and bases.

When Z in the general formula for the said stabilizers is an R group, a di-organotin halide is reacted with one molecular proportion of the mercapto-compound. When Z is an %R group, a mono-organotin halide is reacted with two molecular proportions of one or more of the mercapto-compounds. When Z is a halogen atom, a monoorganotin trihalide is reacted with one molecular proportion of the mercapto-compound. If desired, mixtures of the compounds of the invention may be prepared and employed for the purposes stated, for example by reacting a mono-organotin trihalide with between 1 and 2 molecular proportions of the mercapto-compound. When Z is an acyloxy group, a mono-organotin trihalide is reacted with one molecular proportion of both the mercapto ccmpound and a carboxylate salt; such reactions may be carried out concurrently or successively in either order. The carboxylate salt employed is usually an alkali-metal salt of the carboxylic acid. The metal halide by-product is removed by filtration or aqueous extraction.

Those of the said stabilizers which may be represented by the formula where R, R and X are as hereinbefore stated and Z is an R, X or SR group, may also be prepared by a disproportionation reaction between an organotin mercaptide of formula R,. Sn(SR') (wherein a is 1 or 2) and at least one tin halide of formula R SnX (wherein b is 0, 1 or 2). Thus the tin halide may be a monoorganotin trihalide RSnX a diorganotin dihalide R SnX and/ or, when appropriate, a stannic halide SnX Such reaction is conveniently carried out merely by heating the reactants together in substantially the appropriate stoichiometric amounts to a temperature of from 50 to 200 C., a preferred temperature being 70-l00 C.; an inert diluent such as a hydrocarbon or ether may be present, if desired. The appropriate stoichiometric amount for the reactants for this disproportionation or equilibration reaction depends upon the nature of the reactants and the product desired, but the choice of reactants and their proportions can readily be determined from the appropriate reaction equations, examples of which are:

When the disproportionation reaction is carried out with an organotin halide reactant, the organo groups bound to tin should be identical with those bound to tin in the organotin mercaptide if a unitary product is desired. The disproportionation reaction normally proceeds rapidly to completion so that little or no purification of the product, apart from any solvent stripping, is needed. Such a disproportionation reaction may also be carried out in situ in the vinyl chloride polymer or copolymer during the milling operation by adding the appropriate mixture of disproportionation reagents thereto.

The particular organotin compounds hereinbefore described find use as stabilizers for vinyl chloride polymers and copolymers (herein defined as those derived from not more than 20% by weight of monomers other than vinyl chloride, for example vinyl acetate and/or vinylidine chloride). In compositions comprising these polymers the stabilizers should be incorporated in an amount of from 0.1 to 5%, preferably 0.5 to 2%, by weight of the polymer or copolymer. It has been found that the addition of these compounds confers a more superior degree of stabilization on the vinyl chloride polymer or copolymer than does a conventional organotin mercaptide stabilizer.

Other stabilizers may also be present in admixture with the present organotin compounds, for instance there may be present similar amounts of organic phosphite and/or thiophosphite esters; and/or fatty acid salts of calcium and/or zinc and/or cadmium and/or barium and/or lead; and/or hindered phenols such as 2, 6-di-tert.-butyl- 4-methyl phenol and 2,4-di-tert.-butyl phenol; and/or basic lead carbonate or stearate. Other organotin stabilizers may also be present if desired. The polymer compositions will often contain one or more plasticisers in conventional amount and may contain other additives conveniently employed, such as pigments and/or extrusion or moulding aids. The polymer compositions of the invention are compounded in conventional manner, for example by calendering or on a two-roll mill.

The invention is illustrated by the following examples in which all quantities are expressed on a weight basis. Examples 1 to 5 illustrate the preparation of novel compounds of the invention and Examples 6 to 16 the compositions of the invention. The term lauryl is intended to refer to the mixture of alkyl groups, present in a narrow-cut coconut oil in which at least 50% of the alkyl groups are dodecyl,

EXAMPLE Dibutyl-laurylmercapto-tin chloride Example 2 was repeated using dibutyltin dichloride EXAM L 1 5 (101.5 parts, 0.33 mol), lauryl mercaptan (67.5 parts 0.33 mole), petroleum ether (B.P. 80-100" C.) (200 ml.) Butyl'dloctylmercapto'tm chlonde and triethylamine (34 parts). There was obtained dibutyl- Monobutyltin trichloride (94.2 parts, 0.33 mol) was laurylmercapto-tin chloride, mixed with n-octyl mercaptan (97.3 parts, 0.66 mol) and heated to 60 C. Triethylamine (67.2 parts, 0.66 A ES 6-9 mol) was added to the stirred mixture during 30 minutes u while the temperature was maintained at 6065 C. Water Rrgrd ,polyvrrryl eh'lorrde. stock Sheets were Prepared 50 ml.) was added to dissolve the amine hydrochloride. by l g a vmyl dlsperswn q r P Wlth The organic layer was separated and stripped to 100 stearre Part) and stabrheer Parts) a C. internal temperature at apressure of 14 mm. Treatment j e at 155 for 10 mrrmres- The rellewmg of the product with a filter aid followed by filtration Stablhzers were used: yieldedlbugyl-dfictyllmercapto-tm chloride (115 parts) Example 6 Butyl dilaurylmercapto tin chloride; as a C0 our 655 qul Example 71:1 mixture of butyl-dilaurylmercapto-tin EXAMPLE 2 chloride with butyl-laurylmercapto-tin dichloride; Example 8-Butyltin-dioctylmercapto-tin chloride and Mixture of butyl dllaurylmerc-aptolun cl-flonde and Example 9Dibutyl-laurylmercapto-tin chloride; and as butyl-laurylmercapto-tin d1chlor1de a comparative test dibutyltin dilaurylrnercaptide WhlCh Butyltin trichloride (92 parts, 0.33 mol) lauryl meri a conventional stabilizer, captan (101 parts, 0.5 mol) and petroleum ether (B.P. 6040 Q) (260 were mixed and heated to Samples of the stock sheets were aged in an oven (a) Triethylamine (51 parts) was added dropwise while the at 9 for P to 1 l at 190 for up to temperature was maintained at 55-60 C. After cooling 20 rr1rnute5and (e) at 9 for 11P to 20 mmutes- Wrrh the product was thrice washed with Small amounts of each of the examples the initial colour of the stock sheets water, the organic layer stripped of solvent and filtered and Its color arrer r agerng treatment were less than as in Example 1 to yield an equimolar mixture of butylthat or the eomparatrve test- 1 1m tallizyhlofirgipto tm d1chlor1de and butyl dilaurylmercapto EXAMPLES 1O 13 EXAMPLE 3 Stock sheets of rigid polyvinyl chloride were prepared Octyl-laurylmercapto-tin dichloride by milling the following formulations on a two-roll mill Octyltin trichloride (68 parts, 0.2 mole), lauryl merat for 5 mmutes' Parts captan (40 parts, 0.2 mole) and petroleum ether (B.P. s0-100 c. 100 ml.) were mixed, heated to c. and g f f i f 13-559) triethylamine (20 parts) added as in Example 2.and 40 ace 0 (u meant) d "E7 the mixture stirred for a further /2 hour. The amine epoxy eff g' i llzer) hydrochloride was removed by filtration and the filtrate rganotm Sta 1 lzer as per a e stripped of solvent to C. at 14 mm. pressure. There The resulting sheets were cut into strips and aged in was obtained octyl-laurylmercapto-tin dichloride (97.5 a press at 175 C. Table I below indicates the colors of parts) as a very pale yellow liquid. the samples after dilferent ageing periods.

TABLE I Ageing period at C. in minutes Example Stabilizer 5 15 30 60 Comparative Dibntyltin dilauryl mereaptide Pale yellow- Yel1ow- Yellow Yellow. 10 Butyl-di-lauryhnereapto-tin chloride. C0l01'less Colorless Very pale yellow Pale yellow brown. 11 1:1 mixture of butyl-lauryl-mercapto-tin dichloride and butyldo d0 d0 Pale yellow.

dilauryl-mercapto-tin chloride. 12 Octyl-dilauryl-mercapto-tin chloride d0 do do Yellow brown. 13 Butyl-dioctyl-mereapto-tin chloride do d0 Very pale brown Pale brown.

The examples each indicate that these compounds con- EXAMPLE taining tin-carbon, tin-halogen and tin-sulphur-carbon Butyl-dilaurylmercapto-tm chloride bonds are superior stabilizers to a conventional organo- Monobutyltin trilaurylmercaptide (124.2 parts) was 70 m1 mereaptlde Stabllllefequilibrated with butyltin trichloride (22.6 parts) by heating them together at 80 C. for 1.5 hrs. As a result of EXAMPLES 14-16 this disproportionation reaction there was produced butyldilaurylmercapto-tin chloride (Found: Sn, 19.5; S, 9.7; The technique of Examples 10-13 was repeated with Cl, 5.8%; Calc. for C H ClS Sn; Sn, 19.4; S, 10.4; C1, 75 the following formulation and with the ageing carried out in an oven at C.

Parts Polyvinyl chloride (Corvic D-559) 100 Stearic acid (lubricant) 0.5

Organotin stabilizerin amount and as specified in Table II.

8 3. Butyl-dilaurylmercapto-tin chloride. 4. Butyl-laurylmercapto-tin dichloride. 5. Octyl-laurylmercapto-tin dichloride. 6. Octyl-dilaurylmercapto-tin chloride. 7. Dibutyl-laurylmercapto-tin chloride.

TABLE II Ageing period at 170 C. in minutes Amount of Example Stabilizer stabilizer 30 60 Comparative Dibutyltin dil uryl mercaptide 2.0 Very pale yellow Yell0w Dark yellow. 14 1:1 mlxture of butyl-diluuryl-mercapto-tin chloride and butyl-lauryl- 1. 64 Colorless C0l0rless Very pale brown.

mercapto-tin dichloride. 15 Butyl-dioetyl-mercapto-tin chloride 1.6 do do Very pale yellow. 16 As in Example 14 2.0 do do... Do.

Again these examples illustrate the superiority of the compounds containing carbon-tin, tin-halogen and tinsulphur-carbon bonds as stabilizers for polyvinyl chloride.

I claim:

1. The compounds having the general formula i RSl!1-SR2 wherein R is an alkyl group having up to 20 carbon atoms, X is chlorine, R is an alkyl group having at least 5 carbon atoms and Z is selected from the group consisting of R, X, SR' (where R is an alkyl group having 5-20 carbon atoms).

2. Butyl-dioctylmercapto-tiu chloride.

References Cited UNITED STATES PATENTS HELEN M. MCCARTHY, Primary Examiner W. F. BELLAMY, Assistant Examiner US. Cl. X.R. 260 .75 

